1. Field of Invention
The present invention relates to quality control procedures and apparatus for testing the seal integrity of cannisters such a food and beverage containers.
2. Description of the Prior Art
A high degree of quality control is essential to containerization of food products for retail marketing. Such containers are frequently formed, filled and sealed on a continuous and automatic process line. Consequently, testing for cannister construction and seal integrity is a problematic procedure of extracting samples from a continuous process line for detailed examination. The greater the number and frequency of sampling, the greater the test reliability. To support high production rates, the test must be rapid and reliable as well.
For seal integrity, a test usually involves a gas pressure measurement such as that taught by U.S. Pat. No. 4,555,935 to K. Elert or a flexure measurement of the filled and sealed product such as that taught by U.S. Pat. No. 2,960,223 to F. E. Fauth. With traditional metallic containers, many years of experience have proven the reliability of such tests. However, as new container materials such as plastics and paper have emerged, testing procedures and equipment developed for metal containers are being found inappropriate for the new materials. For example, when a metal cannister is subjected to a pressure differential, whether an internal pressure or vacuum, structural distortion is immediate. Under the same pressure differential condition, structural distortion of a paper cannister is a delayed creep.
It is, therefore, an object of the present invention to provide a rapid and reliable seal integrity test procedure for containers that have a delayed distortion response to a pressure differential.
Another object of the invention is to provide an apparatus that will rapidly and reliably test a number of delayed distortion response containers simultaneously.
Another object of the present invention is to provide a semiautomatic container testing procedure and apparatus.